1. Field of the Invention
The present invention relates to a display device which is useful when applied to various kinds of devices such as a watch, a calculator, a cellular phone, and meters of a car, and a manufacturing method of the same.
2. Description of Related Art
With regard to electronic watches, there have been digital watches based on earlier development which electro-optically display information, e.g. time, by using a display device, and the displayed information can be seen from outside a watch case through a watch glass. The display device includes a liquid crystal display element, and is provided inside the watchcase such that it corresponds to the watch glass attached to the watchcase.
The display device used in such electronic watches comprises a liquid crystal display element which includes: a transparent electrode provided on each of opposed surfaces of a pair of upper and lower transparent substrates; a liquid crystal provided between the pair of substrates; and a polarizer provided on the top surface of the upper substrate and the bottom surface of the lower substrate. A semi-transmissive reflector, a fluorescent layer and a backlight element are disposed in this order beneath the liquid crystal display element. The fluorescent layer is one that generates fluorescence in the visible light range in response to light in the ultraviolet range, and is provided on the bottom surface of the semi-transmissive reflector. The backlight element is an element of a surface-emitting type such as an EL element (electro-luminescence element), and light emitted therefrom is transmitted through the fluorescent layer and the semi-transmissive reflector to illuminate the bottom surface side of the liquid crystal display element.
With this kind of display device for an electronic watch, external light enters through a watch glass in a light place, and the external light is transmitted through the liquid crystal display element. A part of the transmitted light is reflected by the semi-transmissive reflector, whereby information such as time becomes visible. The external light other than the reflected light is transmitted through the semi-transmissive reflector, and the fluorescent layer is irradiated with the transmitted light. The fluorescent layer is caused to emit light by light in the ultraviolet range contained in the external light, with which the fluorescent layer has been irradiated. The liquid crystal display element is illuminated also by the light emitted from the fluorescent layer, and the information can therefore be displayed brightly. In case of a dark place, when the backlight element is caused to emit light, the emitted light is transmitted through the fluorescent layer and the semi-transmissive reflector, and the bottom surface side of the liquid crystal display element is irradiated with the transmitted light. The information displayed on the liquid crystal display element thus becomes visible even in a dark place.
In such a display device, in case of a light place, external light is reflected by the semi-transmissive reflector, and fluorescent light in the visible light range is emitted by the fluorescent layer due to light in the ultraviolet range contained in the external light to illuminate the liquid crystal display element. In case of a dark place, the backlight element is caused to emit light to illuminate the liquid crystal display element. Information displayed on the liquid crystal display element thus becomes visible in both light and dark places. However, the information on the liquid crystal display element is displayed only two-dimensionally. Therefore, the mode of display is simple and not really decorative.
Meanwhile, a display device for a timepiece in which a hologram sheet is provided on the back surface side of a liquid crystal display element, and image information of the hologram sheet is represented three-dimensionally, has been known.
With such a display device, however, information displayed on the liquid crystal display element cannot be represented three-dimensionally, although the image information of the hologram sheet, which has been formed thereon beforehand, can be represented three-dimensionally. Moreover, use of the hologram sheet involves a problem that the manufacture thereof is difficult and cumbersome, and the display device is accordingly expensive.